The Juvenile Instructor began publication in January 1866 and was the first children's magazine published between the Mississippi River and the West Coast of the United States. Its first issue identified its primary audience as the children of The Church of Jesus Christ of Latter-day Saints, and its purpose was to help prepare them for future responsibilities. It was originally published as a 10 1/2 by ­15 1/2 inch four-page, three-column, semimonthly publication.

The magazine was initiated, owned, edited, and published by Elder George Q. Cannon until shortly before his death in 1901. During his lifetime he was the general superintendent of the Church's Sunday School, a member of the Quorum of the Twelve Apostles, a Counselor in the First Presidency of the Church, and also a territorial delegate from Utah to the U.S. Congress. The Juvenile Instructor published editorials, poetry (some by Eliza R. SNOW), and a monthly column, "Voices from Nature," by Karl G. Maeser (president of Brigham Young Academy, later Brigham Young University). It also printed essays, stories, and biographical sketches that often focused on moral issues or the history of other cultures. Officially owned and published by the Sunday School from 1901 to 1929, the Juvenile Instructor contained important organization and business matters of the Sunday School as well as adult and youth stories and essays. As its interests turned more toward filling the needs of teachers, it became the teachers' magazine of the Church and was renamed The Instructor in 1929.